In the medicine of today punctures are daily routine measures. Punctures have many purposes: diagnostic, therapeutic, nutritive etc. Most refer to access to the circulation system for sampling or to establish an intravenous access. The others refer mainly to single injections, which may be intravenous, intramuscular or cutaneous.
At intravenous access the puncture needle has no other task than the establishment itself. The cannula needle is removed when the access is secured. In contrast, the needle has a liquid transport function at sampling and injection.
Common for all used puncture needles is that at least their points must be handled as potentially contaminated, as a stab insult under unlucky circumstances may bring life threatening consequences for affected individuals. Thus, a very urgent need for a well functioning and safe point protection for used puncture needles exists.
Unfortunately proposed solutions of the problem have shown to be rather unsuccessful so far. They have been judged as expensive and/or difficult to use.
WO-A1-9101154 refers to a point protection consisting of a tube-shaped envelope provided with outgrowths that attach to the tissues of the patient and pull the envelope forward to cover the needle point, when the needle is drawn out. Superficially, this may seem to be an elegant problem solution. However, closer scrutiny gives a poorer result.
Contrary to what is said in the publication, the outgrowths will unavoidably increase the patient""s discomfort from the puncture. As many patients experience punctures as traumatic even under normal circumstances, this is very unwanted.
More serious is the fact that a design according to the cited publication puts contradictory and unrealistic demands on fit-up and gauging of the envelope and the needle. The fit-up must be firm and the length of movement of the envelope must be sufficient to avoid too early activation of the protection. Simultaneously the envelope must slide easily and the distance must be short not to cause the patient that the firmness of the patients tissues varies and that plastic that is the only realistic material for the envelope varies very much regarding shrinkage etc. and one realises easily that the manufacturing and quality problems become insuperable.
A probable consequence of this is that the function of the protection becomes very haphazard. At the same time the existence of the protection gives the operators a false sense of security. The combination of these facts may increase instead of decrease the frequency of insults.
Another important drawback is that the protection cannot be activated before the needle is drawn out. Beside the mentioned insults caused to the patient by the very shield comes that the needle point after the initial puncture of the vessel wall still is unprotected and may easily cause unwanted insults during the time the handling needs to ensure that the final position is reached.
EP-A1-0356810 refers to a protection consisting of a tube-formed metallic shield or envelope with a blunt end. The protection is activated at the delivery and deactivated by screwing down to press a compressible elastic body together. After use the protection is reactivated by screwing in opposite direction to let the elastic body expand and move the shield forward over the needle point.
Probably protection of this kind will also increase rather than decrease the insult risk as it demands a succession of complicated movements close to the sharp and in the final stage bloody needle. Another serious drawback is that the protection has to remain deactivated, while the needle is put aside, when the puncture area is put in order, if the operator does not have assistance to take care of the needle immediately.
The protection according to this earlier publication differs from puncture needles according to this application by being activated before the use. Thus, its fixation in active position cannot be irreversible.
EP-A1-0657184 refers to a needle point protection consisting of a rod (or a tube) with a blunt end that may be moved forward and backwards within the cannula-formed, sharp-edged needle. In one of the three principally different designs the protection it is activated at delivery and deactivated by pressing two wings together at the use. The handling of the needle is complicated by the deactivation arrangement. The protection is reversible and the risk large that the combination of needle and protector at handling after use may get jammed so that the activation is neutralised. Thus, this type of protection implies a false security that may lead to carelessness at the handling of the dangerous waste that used needles are and in this way increase the insult risk.
In another design, which can be used for injection syringes only, the rod has a double function and serves simultaneously as an injection plunger. Of course, this will imply important limitations upon injected volume. In this design the protection activation may be made irreversible. The double function as injection plunger implies that only a solid rod can be used. In this way this earlier publication differs from this application that refers to designs with thin walled tubes or hoses.
In a third design, intended for the placing of catheters, the protective rod is fastened to a body that has an elongated projecting impact part at its opposite end. At activation this impact part is struck against a hard surface to bring the protective rod forward to an irreversible protective position. The activation requires 1. Removal of the needle body, 2. Turning of the needle body, which probably requires grip changing, 3. A comparatively hard stroke against a suitable surface. Probably all this must wait until the operator has put the puncture area in order and has both hands free. During this time the needle will be lying unprotected. The activation demands handling close to the needle point. Again a protection of this kind may be expected to increase rather than decrease the injury risk by that a) the existence of protection gives a false sense of security when the protection activation becomes haphazard, b) the handling close to the needle point increases the risk that the operator under stressed conditions misses and injures her or his own hand.
The inventor behind this application has experience of many years of emergency treatment of different kinds and has, guided by this experience, compiled the following demand profile of functioning hypodermic needle protection.
1. The activation of the protective function should not require more work and/or more time as the work situation is characterised by hustle and stress already.
2. If the activation is voluntary it should be a natural part moment that does not require any special attention.
3. Adding of the protective function to the equipment should not require design changes that make changing of habitual grips and handling routines necessary.
4. Use of equipment with built in protective function should not cause more discomfort for the patient than that which is unavoidable due to the puncture itself.
5. The activation should not require hand grip in front of or close to potentially contaminated needle points.
6. Activation of the protective function should be possible latest in the stage, when the needle is drawn out, i.e. before the operator has to put the puncture needle with accessories away to take care of the putting the puncture area in order.
To these very strong xe2x80x9cshouldxe2x80x9d a couple of weaker but important ones have been added.
1. Activating should be possible without grip change.
2. For liquid transport needles that are not protected by outside cannulae activation should be possible in the initial stage already, i.e. when the vessel puncture has been carried through to prevent inside injuries at the vessel walls.
3. Reasonable safety for, largely seen, one-hundred per cent, irreversible activation should exist, as otherwise the same strict routines as before have to be applied.
None of the earlier proposed solutions come near of fulfilling this demand profile.
At the working out of this invention the demand profile has been guiding. The invention starts from a simple, elementary and easily understood principle. Instead of loose accessories, which seldom or with difficulty may be put in place without both hands, a built-in point barrier in the used equipment is proposed. A well known and painful experience exists that desirable and available protective arrangements often remain unused due to troublesome application procedures.
The point protection of the invention consists of a thin-walled tube or a thin walled hose of suitable length fitted outside or inside the puncture needle and automatically or manually movable, with hand grips at safe distance from the needle point, from a not activated rest position to an activated, irreversible protective position, where the front end of the protector is fixed a few millimetres in front of the needle point to eliminate the risk of stab or scratch injuries from the sharp needle point.
That the handling shall be possible at safe distance from the needle point and potentially contaminated parts shall be interpreted in the way that under no circumstances the handling shall have to be done so it brings the hand in front of the needle. Instead the grip point should lie clearly behind the part of the needle that has been inside the patient""s tissues and thus is potentially contaminated. Further the hand grips for activation should be such that possible fumblingness or slipping does not bring the hand in front of the needle point.
It should be noted that a protector according to this invention, which does not use the patient""s own tissues for protection activation, must be pushed forward over the needle point by a force applied from behind. This in contrast to the protection according to WO-A1-9101154, which is drawn forward by a force caused by the outgrowths attaching to the patient""s tissues and causing a pulling force applied at the front part of the needle protection.
That the tube (or hose) is thin walled means that its wall thickness is smaller than its inner diameter. The wall thickness becomes of course dependent of the needle diameter and the material chosen for the protector. For very rigid materials, such as stainless steel, a wall thickness of xcx9c0,01 mm may be quite sufficient. For plastic material larger wall thickness may be required, for instance 1 to 2 mm and for very thick needles even up to 3 mm. In the cases where the muzzle end of the protector is used for the fixation of the irreversible protective position a local wall thickening of up to 2 mm or more may show to be appropriate even for thin needles.
The point protector is at delivery mounted upon the needle in what is called rest position in this description. This rest position is chosen so that use and function does not get obstructed. Fixation to protective position must be adequate and may be controlled either by a suitable arrangement at the surface of puncture needle itself or at the surface of the needle body. Another possibility is fixation backwards with the aid of the front end of the needle and forward by a stocking of suitable length.
A reliable mechanical point protector is a fundamental prerequisite for protection against serious contagious inoculation. Added to this comes the desideratum to avoid exposure of contaminated surfaces for touching when taking care of the needle after finished use.
This desideratum is easiest to fulfil for the puncture needles for intravenous access. This will be obvious from the following description of different embodiments of the basic idea.